This shade sail installation video is for installing an eXcite shade sail using the ‘inline’ turnbuckle, this gives the installer more controls for tensioning the sail. See also the DIY Tip Installing your shade sail.
A good shade sail installation requires tensioning by the corners to the fixing points and it also requires tensioning of its edges. The edge of the shade sail is supported by the hollow that is cut into the sail during manufacture and the tensioning of the perimeter wire by the inline turnbuckle during installation.
A shade sail installation that has good tension on the perimeter wire looks better because it flatens the sail out so that it is not baggy in the center.